Watching the episodes in the recently released DVD set of the 2008-2009 20th season of The Simpsons prompted thoughts that the show made good use of the elements that contributed to its success and that that those elements contributed to its phenomenal longevity.

Like the even longer running Saturday Night Live, The Simpsons recognizes that commenting on current events can help keep a show on the air. Targets from the 20th season included kids with cell phones, the mortgage crisis, and local laws that are designed to discourage immigrants from living in a community.

The cell phone episode contains a classic Simpsons line. Marge asks Bart where he got a cell phone that she found him using. He replied “By accident on a golf course; just like you got me.”

In addition to being very funny, Bart’s line conveyed the irreverent attitude that makes The Simpsons so great. This episode is noteworthy as well for reintroducing the gag of Bart calling bartenders asking for people with fake names, such as Homer Sexual, that had been absent for many seasons.

The fact that the couch gag in the opening credits of the first episode was a Star Wars parody was the first sign that the show was additionally going to continue its practice of referring to films; a later couch gag in the season was a tribute to The Wizard of Oz.

The good news is that we can all relate to poking fun at movies, and The Simpsons does a great job with this type of humor. The bad news is that the show further resorted to several blatant rip-offs of movies in its 20th season, but doing so is forgivable given the age of the program.

The most blatant rip-off is a parody of the story of the prince and the pauper in which Bart switches places with a wealthy look-alike. Despite the unoriginal plot, a nice element of The Simpsons is added and the episode has amusing moments.

Another episode has Marge and Homer ala The Slums of Beverly Hills renting the most run-down apartment that they can find in ultra-wealthy Waverly Hills so that Bart and Lisa can attend school there. Much of the humor in this one comes from parodying teen idol Hannah Montana.

A third episode in which Lisa enters a crossword puzzle contest is very similar to the documentary Wordplay that depicts this type of competition. This episode does a great job showing the obsession of crossword fanatics, offers one of the most clever ways that Homer has made up for disappointing Lisa, and allows fans of the New York Times crossword puzzle and the NPR weekly puzzle challenges to see an animated version of Will Shortz.

Another highlight of the season includes a episode with the deceased Maude Flanders, who does not play a ghost.

I must express my disappointment at the lack of a Sideshow Bob episode; these are even better than the Treehouse of Horror shows.

The packaging of the DVD set is the same as the episodes itself in that it has many strong elements with a few flaws; the discs are housed in fold-out packaging that presents a collage of seemingly every Simpsons character from the past 20 years. I found Homer’s long-lost brother “uncy” Herb, Bart’s pet elephant, and living and dead versions of Maude Flanders easily but could not locate incompetent attorney Lionel Huntz, who The Simpsons retired when Phil Hartman passed away, or dog trainer Emily Winthrop who Tracey Ullman voiced; I am sure that they are there somewhere.

The only real disappointment with the set packaging is that the booklet that contains episode descriptions lacked the amusing message from Simpsons creator Matt Groening that is usually included.

Groening’s message in the first set was prophetic in saying that fans would buy them every set in DVD format only to later have to buy them in the next new format; the 20th season set was released in blu-ray as well as DVD.